Operation; Wavelengths; Example Of A Titration Curve - Hach PTM450 Manual Del Usuario

Operation

Chemical exposure hazard. Obey laboratory safety procedures and wear all of the personal protective
equipment appropriate to the chemicals that are handled. Refer to the current safety data sheets
(MSDS/SDS) for safety protocols.
Do a titration
Do the steps that follow to complete a titration.
1. Prepare the titration system. Refer to the titration system and the application working procedure
documentation.
2. Make sure that the titration module and the probe are correctly installed and connected.
3. Install the probe on the electrode holder.
4. Connect the titration module to the legacy adapter of the titration system. Follow the instructions
that show on the TitraLab AT1000 to set up the legacy adapter.
5. Select the applicable wavelength on the module 3-position switch: 525 nm or 610 nm based on
your application working procedure.
Usually, select the wavelength that is non-absorbing for the coloured solution at the titration start
then absorbing for the color after the end point. Refer to
6. Use the titration system and the instructions on the application working procedure to complete the
titration.
Indicator
Calmagite
Eriochrome black T
pH indicator
Helianthin
Phenolphtalein

Example of a titration curve

In the example, complexometric titration with EDTA at pH = 10 is used to determine the total
hardness of a mineral water. The equivalent point is find with colorimetric detection. The change in
color (wine red to blue) causes a potential jump of 600 to 800 mV and an accurate and reproducible
definition of the equivalent point (standard deviation around 1% on the 3 tests). Refer to
8 English
Table 1 Wavelength selection based on indicator
Non complexed form
Red
Red
Table 2 Wavelength selection based on pH indicator
Colour = f (pH)
red = <3.1
orange = 3.1 to 4.4
yellow = > 4.4
no colour = <8.3
pink = 8.3 to 10
purple = >10.0
D A N G E R
Table 1
Complexed form
Blue
Blue
and Table 2.
Wavelength
610 nm
610 nm
Wavelength
525 nm
610 nm
Figure 3.